how to convert observable to array ? angular4

Question

post has a type observable not array , I need a help

Answer 1

Use the async pipe

<div *ngIf="(posts | async).length > 0"></div>

to get the values for the current emit of your Observable.

Answer 2

Would like to improve previous ans.. async pipe itself check for null or undefined value therefore no need to check .length>0 . So improved answer would be

*ngIf="(post | async)"

or another way is

*ngIf="post.value.length>0"

Hope this will help you :)